A growing number of pupils are taking pictures up teachers’ skirts and posting them on social media, unions in Wales have warned.

The “disturbing“ increase in upskirting and “downblousing” – taking a photograph down someone’s top without their permission – was raised at the National Association of Schoolmasters Union of Women Teachers’ (NASUWT) conference in Wrexham.

Sion Amlyn, a national executive member of the union, said: “Quite disturbingly there’s an increase in the practice of upskirting or downblousing by pupils on teachers and that has a detrimental effect on the wellbeing of our members.

“They suffer from depression, they don’t want to go back to work again and more needs to be done to tackle this kind of practice.

“Schools are trying. There are mechanisms in schools to tackle this but I don’t think they are being used properly or adequately enough.”

It comes after Theresa May announced the government would introduce a law to ban upskirting after a previous attempt to introduce a ban was blocked by MPs earlier this week.

Sir Christopher’s actions led to outrage and embarrassment for other Tories who backed the bill, and women’s underwear was hung from the doors of his offices in protest on Monday morning.

The new law would mean the offence carries a maximum two-year sentence and, in the most serious cases, allows those convicted to be placed on the sex offenders’ register.

Under current law, there is no specific offence naming and banning upskirting in England and Wales, with victims and police only able to pursue offences of outraging public decency or as a crime of voyeurism.

It comes after a study by NASUWT in March revealed that four in five (81 per cent) of teachers said they believed they had suffered sexual harassment or bullying in the workplace since starting the profession.